Content protection systems, such as High-bandwidth Digital Content Protection (HDCP) compliant systems, securely transmit digital content from a source device (e.g., set-top box, optical disk player, notebook computer) to a receiver device (e.g., high-definition television) via high-bandwidth interfaces (e.g., HDCP-protected interfaces) and possibly via one or more intermediary repeater devices. The protected digital content may include, for example, compressed or uncompressed digital video data included on a digital versatile disk (DVD) or in a transmission of cable content. HDCP techniques are described in various HDCP Specification versions (e.g., HDCP 1.3, HDCP 2.0).
Before transferring content from a source device to a receiver device, however, the source device may need to first authenticate the receiver device is eligible to receive the content. This authentication may be based on the receiver device's secret keys and identification information. For example, each HDCP version 1.x compliant receiver may include a unique identifier such as a unique Key Selection Vector (KSV). The identifier may include any form of identification (e.g., 40 bit sequence, key, etc.) that identifies the device. If an HDCP 1.x receiver device's secret key were compromised, that receiver's privilege to receive HDCP content may be revoked and its identifier (i.e., KSV) may be included on a revocation list found within privilege renewability content, such as a System Renewability Message (SRM) in HDCP systems. Privilege renewability content includes content that may be used to update whether a device or group of devices continues to be allowed rights or access to certain protected content. SRMs may be delivered to a source device (e.g., DVD player) along with, for example, movie content included on a DVD. Source devices continually check for newly released SRMs, which may be included in newly released DVDs, that include the most up-to-date lists of privilege revoked devices. Pursuant to a DVD player source device's attempt to play the movie on a high-definition television receiver device, the DVD player may receive the television's KSV. The DVD player may then determine if the KSV of the receiver device is found in the SRM that was included in the newly received DVD. If the KSV is found in the SRM's revocation list, authentication fails and the DVD player will not send the content to the television.
Release of HDCP 1.x versions have been followed by the release of, for example, a HDCP 2.x specification (e.g., HDCP 2.0). Each HDCP version 2.x receiver may include an identifier, such as a unique Receiver ID similar to a KSV used in HDCP 1.x receiver devices. A compromised receiver's Receiver ID may be included in an SRM that is distributed to source devices. If the Receiver ID is found in the revocation list, authentication between the source and receiver devices fails, the authentication protocol is aborted, and transmission of HDCP content to the receiver device is stopped.
In heterogeneous systems which have both HDCP 1.x and HDCP 2.x receivers, a HDCP 1.x may need to communicate with both HDCP 1.x and 2.x receivers. Thus, a HDCP 1.x source device playing a DVD may need to use a newly updated HDCP 1.x compliant SRM included in a DVD to identify both HDCP 1.x and HDCP 2.x receivers whose HDCP privileges have been revoked. Similarly, a HDCP 2.x source playing that same DVD may also need to use a newly updated HDCP 2.x compliant SRM included in the DVD to identify both HDCP 1.x and HDCP 2.x receivers whose HDCP privileges have been revoked. An interoperable and scalable format for privilege renewability content may allow for continued upgrades or renewals of revocation lists in systems including legacy and newer devices that may be compatible with different versions of content protection systems.